1. Field of the Invention
The present invention relates to universal serial bus (USB) USB chargers and charging circuits for charging the batteries of electronic devices.
2. Description of the Prior Art
Nowadays, there are many brands and designs of smartphones, cellular phones, Internet tablets and portable electronic devices, including the APPLE™ IPOD™, IPHONE™ and IPAD™ devices, the ANDROID™ cellular phone or tablet, and others, that use the DC power source from their internal batteries. The batteries of these devices need to be recharged through a USB port. Although the wiring configuration and charge power (charge voltage and current) allowed for normal operating range of a USB port is specified by the USB Battery Charging Specifications, nevertheless, each manufacturer of USB-compatible portable electronic devices also develops its own charging profile for its devices. The charging profile for each portable device may or may not be the same, and may vary from one device to the other, depending on the manufacturer for each portable device. Since there are several different charging profiles for these USB portable electronic devices on the market, a generic USB charger may not work or be compatible with those devices. Therefore, consumers are forced to purchase expensive USB chargers from the OEM companies for their products.